Spatial vision in the purple sea urchin Strongylocentrotus purpuratus (Echinoidea)
Spatial vision in the purple sea urchin Strongylocentrotus purpuratus (Echinoidea)
复制标题
紫色海胆 Strongylocentrotus purpuratus（海胆总科）的空间视觉
DOI：
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发表时间：
2010
影响因子：
2.8
通讯作者：
Sönke Johnsen
中科院分区：
文献类型：
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作者：
D. Yerramilli;Sönke Johnsen
最近的证据表明，棘球蚴属的棘类动物具有中等的视觉灵敏度，这似乎是由它们的脊柱筛选离轴光介导的，这表明具有较高脊柱密度的海胆可能具有更敏锐的空间视觉。我们分析了39个紫癜标本在放置在一个无特征的容器中心后的运动，该容器内有一个角直径为6.5度或10度的圆形黑色目标（立体角分别为0.01 sr和0.024 sr）。每个海胆的平均方向矢量是通过对动物进行四次测试来确定的，目标依次放置在0度、90度、180度和270度（相对于磁东）的方位上。相对于环境的任何非目标特征或相对于6.5度目标位置的变化，海胆没有明显的单峰或轴向取向。然而，相对于10度目标的变化位置，海胆具有强烈的轴向取向（平均轴从-1到179度；95%置信区间为±12度；P<0.001，摩尔非参数霍特林检验），针对该目标进行测试的20只海胆中有10只选择了距离目标中心或相反方向10度以内的平均方位（两个是偶然的）。此外，10度目标的20个目标归一化方向的平均长度（每个是四个试验的方向的向量和）远远高于偶然预期（P<10−10；蒙特卡罗模拟），表明每个海狗，无论是向目标移动还是远离目标，都具有高一致性。这些结果有力地表明，紫斑紫癜发现了10度目标，要么接近它，要么逃离它。考虑到海胆对6.5度的目标没有反应，很可能10度的目标接近于这个物种的最小可检测尺寸。有趣的是，测量水平面向测试区域的脊柱密度预测了相似的视觉分辨率（ambulacrum的8.3±0.5度和ambulacrum的11±0.54度）。这种相对较低的，但功能性的敏锐度的功能——与鹦鹉螺和马蹄蟹的敏锐度相当——尚不清楚，但考虑到双峰反应，很可能与寻找避难所和躲避捕食者有关。
SUMMARY Recent evidence that echinoids of the genus Echinometra have moderate visual acuity that appears to be mediated by their spines screening off-axis light suggests that the urchin Strongylocentrotus purpuratus, with its higher spine density, may have even more acute spatial vision. We analyzed the movements of 39 specimens of S. purpuratus after they were placed in the center of a featureless tank containing a round, black target that had an angular diameter of 6.5 deg. or 10 deg. (solid angles of 0.01 sr and 0.024 sr, respectively). An average orientation vector for each urchin was determined by testing the animal four times, with the target placed successively at bearings of 0 deg., 90 deg., 180 deg. and 270 deg. (relative to magnetic east). The urchins showed no significant unimodal or axial orientation relative to any non-target feature of the environment or relative to the changing position of the 6.5 deg. target. However, the urchins were strongly axially oriented relative to the changing position of the 10 deg. target (mean axis from –1 to 179 deg.; 95% confidence interval ± 12 deg.; P<0.001, Moore's non-parametric Hotelling's test), with 10 of the 20 urchins tested against that target choosing an average bearing within 10 deg. of either the target center or its opposite direction (two would be expected by chance). In addition, the average length of the 20 target-normalized bearings for the 10 deg. target (each the vector sum of the bearings for the four trials) were far higher than would be expected by chance (P<10−10; Monte Carlo simulation), showing that each urchin, whether it moved towards or away from the target, did so with high consistency. These results strongly suggest that S. purpuratus detected the 10 deg. target, responding either by approaching it or fleeing it. Given that the urchins did not appear to respond to the 6.5 deg. target, it is likely that the 10 deg. target was close to the minimum detectable size for this species. Interestingly, measurements of the spine density of the regions of the test that faced horizontally predicted a similar visual resolution (8.3±0.5 deg. for the interambulacrum and 11±0.54 deg. for the ambulacrum). The function of this relatively low, but functional, acuity – on par with that of the chambered Nautilus and the horseshoe crab – is unclear but, given the bimodal response, is likely to be related to both shelter seeking and predator avoidance.